The internet has become a medium for the display and playback of various forms of content objects. As used herein, “content object” can refer to digital text (such as a document, a poem, a book, an article, a spreadsheet, and the like), a digital image (such as a digital version of a photograph, a painting, a drawing, a computer-made image, and the like), digital video (such as a digital feature film, a home-video or other amateur-captured video, a music video), a digital sound recording (such as a digital song, a speech, or any other audio clip), a digital animation (such as a .GIF animation, a cartoon, still-motion video, and the like), or any other form of content that is displayed, viewed, or played on a user device over the internet.
Content hosting services on the internet allow users to access content on the content hosting services for display and playback. Content hosting services can allow users to upload content objects to the content hosting services. The content objects uploaded by users may be user-generated content objects. Content hosting services can also retrieve content objects from other entities, such as professional movie studios and music studios, libraries, and the like. One example content hosting system allows users who are artists to upload images of real-world physical artwork created by the user or images including digital artwork created by the user.
Content objects can be organized within a content hosting service in a number of ways. Commonly, tags (labels) are used to categorize content objects. Tags can be taxonomically and hierarchically structured, with varying levels of tag domains. For example, for an art-based content hosting service can use a tag taxonomy with a top level “medium” tag (describing a content object's type of artwork, such as “oil painting”, “water color”, “photography”, and “sculpture”), followed by a next level “genre” tag (describing the a content object's subject matter), a “style” tag (describing the artistic style of a content object), and so forth.
In a content hosting service with a large number of content objects, the manual creation of tags and tagging of content objects by editors or operators of the content hosting service becomes infeasible. Accordingly, many content hosting services prompt users to tag content objects that they upload or content objects uploaded by others. Users may incorrectly tag content objects, for instance by providing an incorrect tag for the medium or genre of an artwork, or may complete only a portion of a content object's tag taxonomy, for instance by failing to include a designation of the style of a content object.
In order to improve the accuracy and completeness of tagging, a content hosting service can present recommended tags to a user during tagging. The space available in a content hosting service interface displayed to a user for displaying relevant tags may be limited. In a content hosting service with a deep tag taxonomy or a high number of tags (for instance, hundreds or thousands of tags), the limited space in a content hosting service interface increases the need to select the most relevant tags for recommendation to a user. Similarly, a content hosting service can present recommended tags to a user during the browsing or searching of content objects to improve the user experience, but limited interface space creates the need to select the most relevant tags for recommendation.